Fluid end for a plunger pump

ABSTRACT

An improved cylindrical fluid end construction for a plunger pump includes a cylinder body, a crossbore body, and suction and discharge valve cages. The components are assembled together by quick-disconnect couplings having self-energizing seals for pressure sealing the joints. The diameters of flow passages formed in the crossbore body are less than that of the pump plunger.

United States Patent 11 1 1 111 3,801,234

Love et al. Apr. 2, 1974 54] FLUID END FOR A PLUNGER PUMP 3,203,3578/1965 061mm 137 454.4 x

[75] Inventors: William W. Love; Everett l-l. Lock; 3532 a] I WilliamJoe 3,620,653 11 1971 Gaylord et al. 417/568 lleilhecker, all ofHouston, Tex.

[73] Assignee: Esso Production Research Company,

Houston, Tex.

Filed: May 14, 1973 Appl. No.: 359,806

Related US. Application Data Continuation'in-part of Ser. No. 179,705,Sept. 13, 1971, abandoned.

US. Cl 417/454, 92/128, 137/5155, 4 17/569 Int. Cl. F04b 39/14 Field ofSearch 417/437, 454, 568, 569, 417/570, 571, 572, 567; 92/128; 137/515,

[5 6] References Cited UNITED STATES PATENTS 3,135,219 6/1964 Hayes etal. 417/454 X Primary ExaminerC. J. Husar Assistant Examiner-Leonard E.Smith Attorney, Agent, or Firm-Robert L. Graham [57] ABSTRACT 6 Claims,4 Drawing Figures PAIENIEBAPR 21914 3Q801234 sHr10r3 WILLIAM W LOVE'EVERETT H. LOCK WILLIAM C. MAURER JOE K. HEILHECKER INVENTORS ATTORNEYPAT APR 21914 I 1801.234

3 SHEEIZGFS I :g 35 v 3? FIG.3

WILLIAM W. LOVE EVERETT H. LOCK WILLIAM C. MAURER JOE K. HEILHECKERINVENTORS AT TORNE Y FLUID END FOR A PLUNGER PUMP CROSS REFERENCE TORELATED APPLICATION This application is a Continuation-In-Partapplication of Ser. No. 179,705, filed in the United States PatentOffice on Sept. 13, 1971, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an improved fluid end construction for a plunger pump.

2. Description of the Prior Art Multiplex plunger pumps are used in avariety of oil field operations which require the pumping of fluid athigh volumes and at high pressures. In many of these operations, it isimportant that the pumps be capable of operating for relatively longperiods of time and that when failure does occurthe pump be capable ofrepair with a minimum of shutdown time. Experience with plunger pumpshas shown that the failure generally occurs in the fluid end of thepump. A recent improvement in plunger pumps involves a sectionalizedconstruction wherein the components of the fluid end are made separatelyand assembled together as a unit. The sectionalized construction offersseveral advantages over the conventional monoblock fluid end. It permitsthe valves to be mounted externally of the main body thus simplifyingthe flow passages through the body which results in fewer stressconcentration points. The sectionalized construction also reduces thecost of the structure since the separate castings or forgings are muchsimpler. Moreover, the sectionalized construction reduces pump repaircosts since only the worn component need be replaced..The maindisadvantage of this type of construction is that it requires severalmore joints. These joints present points of weakness in the assemblybecause of the inability of the couplings to withstand the fluctuatingloads for long periods of time. The components of the sectionalizedfluid end, heretofore, have been assembled by flange connections whichemploy face seals to pressure seal the joints. These flange connectionshave not proven entirely satisfactory in plunger pumps operated at highpressures for long periods of time. The fluctuating load associated withthe plunger pump tends to loosen the bolts and/or damage the seal.Moreover, the flange connections result in a heavy bulky structure sincethe flanges must be capable of exerting high load on the face seal toattain a pressure seal at the joint. The heavy, bulky structure not onlyincreases the cost of the fluid end construction, but requires aconsiderable amount of time and effort to replace worn valves or seals.

As mentioned previously, plunger pumps are used in certain operationswhich cannot tolerate long shutdown periods. For example, during thedrilling of wells by rotary drilling methods, it is hazardous tointerrupt the circulation of drilling fluid through the drill string andup the annulus for long periods because of the risk of sticking thedrill string in the well. The drilling fluid flowing up the wellboreannulus prevents the accumulation of solids in the annulus which couldcause the drill string to become stuck. It will thus be appreciated thatwhen pump failure occurs, the pump should be capable of repair with aminimum shutdown period.

Another example where long shutdown periods cannot be tolerated is foundin fracturing operations. A

fracturing fluid laden with particulate propping agents must be pumpedinto the formation at a minimum velocity to prevent the propping agentfrom settling. If this minimum velocity is not maintained, the sandsettles out of the carrier fluid, accumulates in the wellbore, and plugsthe formation. Here again, the shutdown period for pump repair should bemaintained at a minimum.

In plunger pumps, failure generally occurs in the valve assembliesbecause of the cyclic operation of the valve and because of the highstresses between the valve and valve seat. In the conventional monoblockfluid end construction, the valve assemblies, located internally of thecylinder block, are not readily accessible and therefore generallyrequire several hours to replace. Even in the sectionalized fluid endconstruction which employ flange connections, valve replacement cannotbe quickly performed.

SUMMARY OF THE INVENTION coupling means for assembling the variouscomponents of the fluid end structure. A self-energizing seal ringprovides-a fluid-tight sea] at the joint, and a quickdisconnect.clamping collar maintains the parts in assembled relation. As usedherein, the term selfenergizing seal contemplates the type of seal whichis activated by internal pressure. In other words, the contact pressurebetween the seal and the members being joined increases with internalpressure. It should be noted that the effectiveness of such a seal isprimarily due to the internal pressure and not the force exerted by thecoupling. This permits the use of the clamping collar which is designedprimarily to resist the pressure load.The use of clamping collarsinstead of the flange connections substantially reduces the weight andbulk of the structure. Moreover, the combination of the self-energizingseal and the clamping collar resists bolt loosening and seal ringdamage. When it becomes necessary to replace one of the valves, theclamping collar can be quickly disassembled and a new valve cagesubstituted for the valve cage containing the damaged valve. Experiencehas shown that a valve cage can be replaced in about five minutes whichis only a fraction of the time required to replace a valve cage joinedby a flange connection. Because of this quick valve replacement feature,the fluid end construction of the present invention is ideally suitedfor drilling and fracturing operations.

Another feature of the present invention involves use of reduceddiameter flow passages in the crossbore body of the sectionalized fluidend. It is known that in order to reduce the stress concentration at theintersection of the flow passages in the crossbore body, the ratio ofthe body diameter to the flow passage diameter should be in the order offour or more. In most plunger pumps, the flow passages through thecrossbore are sized to receive the plunger reciprocating therein. By

basing'the flow passage size on flow. rate instead of plunger size, theinside diameter and outside diameter of the crossbore body can besubstantially reduced resulting in a much smaller and lighter structure.This not only reduces the cost of the part but permits the multiplexpump to be assembled in a compact structure.

As mentioned previously, the present invention also contemplates the useof valve cages adapted to be mounted externally of the crossbore body byquick disconnect couplings which permit rapid replacement of wornvalves. v

In summary, the fluid end construction of the present invention involvesseveral novel features which individually and collectively offeradvantages over prior art fluid ends. The improved fluid endconstruction provides a compact structure; the clamping collars lend aquick-disconnect feature to the assembly; and the selfenergizing sealsalleviate the damaging effects of the fluctuating load conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational viewshown partially in section of fluid end for a plunger pump constructedac cording to the present invention. 6

FIG. 2 is an enlarged sectional view of the coupling means used to jointhe crossbore body to other components of the sectionalized fluid end.

FIG. 3 is a fragmentary, longitudinal sectional view of the couplingmeans shown in FIG. 2.

FIG. 4 is aside elevational view of a fluid end construction similar toFIG. 1 illustrating a slightly modified form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT a crossbore body 11, a suctionvalve cage 12 and a discharge valve cage 13. The cylinder body 10 issecured to the pump frame 14 and has a longitudinal bore 16 formedtherein. A plunger 17 is mounted in the bore 16, with a packing assemblyshown generally as 18 providing a seal between the cylinder body 10 andthe plunger 17. The forward end of the bore 16 tapers to a reduceddiameter section 19 which, as pointed out below, registers with a flowpassage formed in the crossbore body 11. The plunger 17 is connected tothe power end (not shown) of the pump which reciprocates the plunger 17within the cylinder body 10 between the solid line and broken linepositions shown in FIG. 1. The power end may bea crank-type drive or ahydraulic drive.

The crossbore body 11 has a pair of crossbores or flow passages 21 and22 formed therein. The corners of the flow passage walls in the area ofintersection are rounded to reduce stress concentration points. Sincethe plunger 17 does not enter the crossbore body 11, the flow passages21 and 22 can be sized on the basis of desired volumetric flow raterather than on the basis of the plunger diameter. The flow passages 21and 22 are thus made large enough to prevent the maximum instantaneousvelocity at the desired flow rate from exceeding about 40 feet persecond. Fluid velocities in excess of this limit tend toerode the wallsof the flow passages. Sizing based on the flow rate parameter permitsthe flow passages to be made much smaller in diameter than the plungersize. For most applications the ratio of plunger diameter to thediameter of the flow passages will be 2 or more. The reduced diameterflow passages permit proportionate reduction in the outside diameter ofthe crossbore body 11. In order to minimize stress concentrations on theinternal surfaces of the crossbore body 11, the ratio of the outsidediameter (OD) to the inside diameter (ID) of the crossbore body 11should be 4 or more. Thus by reducing the diameter of the flow passages21 and 22, the outside diameter of the body 11 can be reducedproportionately resulting in a much smaller member. This not onlyreduces the cost of the member-since less material is required bggalsoproduces a smallta mo gompact SilllgtL.

As mentioned previously, the ratio of the plunger diameter to the, flowpassage diameter should be at least 2 to effect substantial reductionsin the size of the crossbore body 11. The reduced diameter flow passagesin crossbore body 11 also affect the efficiency of the plunger pump. Theclearance volume of the fluid end should be as small as possible toavoid substantial reductions in volumetric efficiency. Clearance volumeis the difference between the fluid volumes of the as sembly with theplunger in the solid line and in the broken line position of FIG. 1. Thereduced diameter passages 21 and 22 in the crossbore body 11 provideless clearance volume than the same construction having full openingflow passages.

The flow passage 21 is aligned with section 19 of bore 16 and extendshorizontally through the crossbore The crossbore body 11 is joined tothe other three components of the fluid end construction, e.g. cylinderbody 10, suction valve cage 12, and discharge valve cage 13, by means ofcoupling assemblies shown generally as 23, 24 and 25, respectively.

As shown in FIG. 1, and in more detail in FIGS. 2 and 3, the couplingassembly'23 which joins the crossbore body 11 and cylinder body.10comprises a clamping collar 26 and a self-energizing seal ring 27.Mating hubs 28 an 29 formed, respectively, in the cylinder body 10 andcrossbore body 11 are provided with tapered shoulders 30 and 31 whichare particularly shaped to mate with interior surfaces of collar 26.With the hubs 28 and 29 arranged in mating relationship, the clampingcollar 26 which can be C-shape in cross section en gages the taperedshoulders 30 and 31. As shown in FIG. 2, the collar 26 is splitcomprising collar segments 26a and 26b. The collar 26a and 26b areprovided with mounting ears 33 and 34, respectively, through which passtangential clamping bolts 35.

The seal ring 27 which can be made of steel or other hard alloy includesa rigid rib 36 and two laterally extending lips 37 and 38. The rib 36fits between confronting surfaces of hubs 28 and 29 while the lips 37and 38 sealingly engage internal surfaces formed in the hubs 28 and 29.The metal-to-metal engagement of the lips 37 and 38 on the hub surfacesextends in a transverse direction withrespect to the joint so thatinternal fluid pressure tends to increase the contact pressure betweenthe mating members. This type of seal is known in the art as aself-energizing seal. The function of the rib 36 is to preventovertightening of the collar which could damage the lips 37 and 38. j

The parts are assembled by placing the seal ring 27 between the hubs 28and 29, placing the split collar around the shoulders 30 and 31, andtightening the clamping bolts 35. As the collar segments 26a and 26b aredrawn together, the hubs 28 and 29 are axially thrust together untilthey engage opposite sides of the rib 36. The sealing lips 37 and 38deformably engage the internal surfaces of the hubs 28 and 29,respectively, in attaining the fluid seal thereon. The clamping collar26 thus applies in initial load on the seal ring 27 to deform the lips37 and 38. The self-energizing characteristic of the seal, however,plays a major role in providing and maintaining the fluid-tight seal atthe joint.

The coupling assemblies 24 and are similar in structure to that ofassembly 23. Specifically, coupling assembly 24 comprises a split collar41 which clamps together hubs 39 and 40 formed, respectively, incrossbore body 11 and the valve cage 12. A self-energizing seal ring 42provides a fluid-tight seal at the joint.

The coupling assembly 25 for joining the crossbore body 11 and thedischarge valve cage 13 likewise comprises a split collar 46 clampingtogether mating hubs 43 and 44 formed, respectively, in the crossborebody 11 and the discharge valve cage 13. A self-energizing seal ring 45positioned at the joint maintains the assembly in a fluid-tightrelationship.

From the foregoing it is apparent that the coupling assemblies 23, 24and 25 have in common the clamping collars and the self-energizing sealrings. A variety of clamping collars and self-energizing seals arecommercially available. The coupling and seal arrangement describedabove and depicted in the drawings, is similar to that sold under thetradename Grayloc manufactured by Gray Tool Company. Another type ofcoupling usable in the present invention is the Vickers- Andersoncoupling described in High Pressure Engineering, published by TheChemical Rubber Company, 1971. The Vickers-Anderson coupling is a splitcollar comprising three segments which are held together by tangentiallyextending bolts. This type of coupling can be used with aself-energizing seal ring for joining the parts in a fluid-tightassembly.

The sectionalized fluid end construction assembled by the clampingcollars and self-energizing seal rings offers several advantages overfluid end constructions which employ flange connections. The fluctuatingload As described above, the suction and discharge valve cages 12 and 13housing their respective valve assemblies may be preassembled as a unitand are mounted externally of the crossbore body 11 by thequickdisconnect couplings 24 and 25. The suction valve cage 12 as shownin FIG. 1 is in the form of a split housing comprising members 50 and51. The housing members 50 and 51 are joined together by means of aclamping collar 52 with a self-energizing seal ring 53 being provided atthe joint. The clamping collar 52 engaging mating shoulders 54 and 55maintain the housing members 50 and 51 in assembled relation. Theclamping collar 52 is split with the segments being connected togetherby tangentially extending bolts in the manner previously described. Thehousing members 50 and 51 in combination define an internal valvechamber 56 which contains the valve assembly. The self-energizing sealring 53 which can be a Grayloc sea] as previously described provides afluid-tight seal at the joint. The surface engagement of the seal ring53 on internal surfaces of members 50 and 51 extends transversely withrespect to the joint so that pressure in chamber 56 tends to increasethe contact pressure and thereby provides a self-tightening effect.

The valve assembly mounted in cage 12 is conventional comprising valveseat 57, a skirted valve 58, retainer 59, and spring 60. The valve seat57 and retainer 59 can be press fit, respectively, into members 51 and50 with the spring 60 being positioned between the retainer 59 and valve58 to maintain the valve in a normally closed position.

The inlet end of the valve cage 12 is threaded for connection to asuction line (not shown) by means of a union or other quick-disconnecttype coupling. As mentioned previously, the valve cage 12 dischargesinto the flow passage 22 of crossbore body 11.

The discharge valve cage 13 may be similar in structure to the suctionvalve cage 12 comprising housing members 61 and 62 coupled together'by aclamping collar 63 with a self-energizing seal (not shown) beingprovided by the joint. The valve assembly contained in the dischargevalve cage 13 includes a valve seat, a skirted valve, a retainer, and aspring arranged in the conventional manner. The inlet of the valve cage13 is aligned with flow passage 21. The discharge end of the valve cage13 is threaded for connection to a high pressure line by means of aunion or other quick-disconnect type coupling (not shown).

FIG. 4 illustrates a slightly modified version of the fluid endconstruction which may be useful in designs that present spacelimitations for the externally mounted valve cages. The fluid endconstruction in this embodiment is illustrated in connection with ahydraulic high-pressure intensifier pump which includes a large diameterbarrel or cylinder body 65 having a plunger 66 reciprocably mountedtherein. Plunger 66 extends beyond the rear extremity of cylinder body65 through a suitable packing and connects to a hydraulic power end (notshown). The hydraulic, power end includes a power piston assembly drivenby power fluid from conventional pumps. The piston is substantiallylarger in diameter than the plunger 66. The pumping pressure of anintensifier pump is approximately the power fluid pressure amplified bya factor equal to the ratio of piston area to plunger area.

The high pressure intensifier pumps normally are provided with largediameter plungers, e.g. from about of body 65 and crossbore body 11.Adapter 67 may threadedly connect to body 65 and for purposes of thisinventiom-is considered to be a part thereof. Adapter 67 has a centralopening 68 which has about the same diameter as flow passage 21.Coupling assembly 23 including collar 26 and ring 27 joins the crossborebody 11 to hub 69 formed in adapter 67.

The suction valve cage illustrated as 70in FIG. 4 contains part of thesuction valve assembly. Part of the suction valve assembly is mounted inan enlarged section 71 of the crossbore body 1 l at the entrance ofsuction flow passage 22. Valve seat 57 is mounted in cage 70 and valveretainer 59 is mounted in the enlarged section 71. Valve 58 is urgedinto seating relation on valve seat 57 by spring 60.

The suction valve cage 70 is connected to the crossbore body 11 bycoupling assembly 24 which includes clamping collar 41 and seal ring 42.

Thedischarge valve cage 13 may be similar in construction as suctionvalve cage 70 but preferably includes mated housing members 61 and 62 asshown in FIG. 4. In the former design, part of the valve assembly, e.g.valve seat 72, will be mounted in an enlarged section at the dischargeof passage 21, retainer 73 in the cage 13 with the skirted valve 74being urged into seating relation on seat 72 by a spring 75. In thelatter design, the complete valve is contained in the cage 13 asillustrated. The valve cage which contains the complete discharge valve,however, is the preferred design because damage by erosion in thevicinity of the discharge valve will be on an inexpensive part, e.g.valve cage member 61; The discharge valve cage 13 is connected to 'thecrossbore body 11 by coupling assembly 25 which includesclamping collar46 and ring 45.

The high pressure intensifier pump operates as follow: the plungerreciprocateswithin housing 65 at between about and strokes per minute;fluid is drawn into the plunger bore through the suction valve assemblyand passage 22 and discharged at a high pressure through passage 21" anddischarge valve assembly. Replacement of either valve requires simplydisconnecting the quick-disconnect coupling, e.g. collars'4l or 46,removing the valve cage, inserting a new valve cage, and reconnectingthe coupling.

The following field test demonstrates the performance of the improvedfluid end construction. The power end of a Gardner-Denver Pl 9 triplexpump was provided with three fluid ends constructed according to thepresent invention. The dimensions of each fluid end were as follows;

7% inch Grayloc 7% inch Grayloc L609 inch Grayloc 5% inch Grayloc 55:inch Grayloc L609 inch Grayloc 9% inch Grayloc 9% inch Grayloc 4.063inch Grayloc hubs (39, 40, 43, 44)

collars (41 and 46) seal rings (41 and 45), ID Valve cage couplings hubs(54 and 55) collars (52 and 63) seal rings (53), ID

The pumping conditions were as follows: Strokes per minute Average pumppressure 8,000 psi Fluid pumped Bentonite drilling mud 9.2 lb/gal.

The field test demonstrated that the sectionalized fluid endconstruction of the present invention is capable of handling highpressure fluid for long periods of time. The test also illustrates thatwhen valve failure occurs, the valve cage containing the faulty valvecan be replaced in a very short period of time usually about 5 minutes.This quick replacement feature is particularly important for pumps usedin drilling and hydraulic fracturing operations.

We claim:

1. In a plunger pump, an improved fluid end construction comprising: acylinder'body having a plunger bore formed therein; a plunger mounted insaid bore and adapted to reciprocably move therein; a crossbore bodyhaving suction vand discharge flow passages formed therein, the diameterof each of said flow passages being substantially smaller than ,thediameter of said plunger; first coupling means for joint-g said cylinderbody and said crossbore body wlierein said flow passages are in fluidcommunication with said plunger bore; a suction valve cage containing apart at least of a suction valve; second coupling means for joining saidcrossbore body and said suction valve cage wherein said suction flowpassage is in fluid communication with said suction valve; a dischargevalve cage containing a part at least of a discharge valve; and thirdcoupling means for joining-said crossbore body and said discharge valvecage wherein said discharge flow passage is in fluid communication withsaid discharge valve, each of said coupling means including a segmentedcollar adapted to clamp together the members being joined, and aself-energizing seal ring engaging internal surfaces of each memberbeing joined, the engagement of said seal ring on said surfaces beingsuch that the fluid pressure internally of said seal ring tends toincrease the engagement pressure.

2. The invention as recited in claim 1 wherein the ratio of the plungerdiameter to the diameter of each flow passage being at least 2.

3. The invention as recited in claim 2 wherein'said flow passagesintersect within said crossbore body.

4. The invention as recited in claim 1 wherein each of said valve cagescomprise separable housing members and coupling means for joining thehousing members together, said coupling means including a segmentedcollar adapted to clamp said housing members together and aself-energizing seal ring engaging an internal surface of each housingmember.

5. The invention as recited in claim 1 wherein said discharge valve cagecontains the complete discharge valve.

6. The invention as recited in claim 1 wherein said suction valve cagecontains the complete suction valve.

1. In a plunger pump, an improved fluid end construction comprising: acylinder body having a plunger bore formed therein; a plunger mounted insaid bore and adapted to reciprocably move therein; a crossbore bodyhaving suction and discharge flow passages formed therein, the diameterof each of said flow passages being substantially smaller than thediameter of said plunge plunger; first coupling means for joining saidcylinder body and said crossbore body wherein said flow passages are influid communication with said plunger bore; a suction valve cagecontaining a part at least of a suction valve; second coupling means forjoining said crossbore body and said suction valve cage wherein saidsuction flow passage is in fluid communication with said suction valve;a discharge valve cage containing a part at least of a discharge valve;and third coupling means for joining said crossbore body and saiddischarge valve cage wherein said discharge flow passage is in fluidcommunication with said discharge valve, each of said coupling meansincluding a segmented collar adapted to clamp together the members beingjoined, and a self-energizing seal ring engaging internal surfaces ofeach member being joined, the engagement of said seal ring on saidsurfaces being such that the fluid pressure internally of said seal ringtends to increase the engagement pressure.
 2. The invention as recitedin claim 1 wherein the ratio of the plunger diameter tO the diameter ofeach flow passage being at least
 2. 3. The invention as recited in claim2 wherein said flow passages intersect within said crossbore body. 4.The invention as recited in claim 1 wherein each of said valve cagescomprise separable housing members and coupling means for joining thehousing members together, said coupling means including a segmentedcollar adapted to clamp said housing members together and aself-energizing seal ring engaging an internal surface of each housingmember.
 5. The invention as recited in claim 1 wherein said dischargevalve cage contains the complete discharge valve.
 6. The invention asrecited in claim 1 wherein said suction valve cage contains the completesuction valve.